The present invention relates to manufacturing techniques to produce multifunctional hybrid composites requiring multi-layered preforms and inserts and multiple resins through the thickness of the composite part.
Currently, multi-resin hybrid composite parts are produced through multiple process steps. Starting at the mold surface, each discrete resin/preform or prepreg combination is processed by hand lay-up, automated tow placement, Resin Transfer Molding (RTM), Vacuum Assisted Resin Transfer Molding (VARTM), Seemann Composites Resin Infusion Molding Process (SCRIMP), or other commonly used manufacturing processes. Layers are combined subsequently through co-cure or secondary bonding options.
Various composites manufacturing processes are used to impregnate fiber preforms with resin. Particularly, RTM and VARTM are used to manufacture composite parts. The processes involve the layup of dry reinforcing fibers in fabric, tape or bulk form as a preform in a closed mold environment, subsequently impregnating the preform with liquid resin using positive pressure, as in RTM, or negative pressure (i.e., vacuum) as in VARTM or SCRIMP or a combined form of both. The resin is cured and the part demolded. However, these processes have been limited to a single resin system.
Traditionally, multi-layered parts have been made using only plastics, using processing techniques such as injection molding, blow molding, and co-extrusion. However, these techniques have been limited to plastics without reinforcements.
The method of the present invention, Co-Injection Resin Transfer Molding (CIRTM), offers the potential to reduce cost and improve part performance and quality by using a single-step process while still offering the possibility of producing hybrid parts. The procedure can be applied to several existing manufacturing processes such as RTM, VARTM, or SCRIMP, which have been limited to single resin systems prior to this invention, as further discussed below.
A fundamental advantage of the invention is the ability to produce a multi-layer hybrid composite part in a single manufacturing step to improve performance, increase quality, and reduce costs. The CIRTM technique offers improved performance via co-cure of the materials, improving the toughness and strength of the interface and eliminating defects associated with secondary bonding. The CIRTM technique has several distinct advantages over the prior art:
It offers considerable cost savings by:
(1) reducing cycle times per part, allowing for higher volume production; PA1 (2) reducing manpower costs and increasing quality through a reduction in opportunities for defects to be introduced during the manufacturing process; PA1 (3) reducing the number of processing steps; PA1 (4) reducing the energy needed to run the machinery; PA1 (5) eliminating the need for adhesives and therefore eliminating the need for surface preparation to apply the adhesives and eliminating the set-up and tolerance problems and defects associated with secondary bonding. PA1 (1) reducing emissions, due to the decreased number of steps; PA1 (2) reducing waste in general and allowing for a more efficient use of material; PA1 (3) completely eliminating the need for adhesives. PA1 (1) reducing weight; PA1 (2) improving bonding through co-cure and therefore improving mechanical properties; PA1 (3) allowing for structural contribution from previously nonstructural layers.
Second, it offers considerable environmental advantages by:
Third, it offers a considerable performance advantage by: